Many communications networks provide high bit-rate transport over a shared medium, such as a Passive Optical Network (PON), a cable television coaxial or hybrid fiber/coax (HFC) network, or a wireless network. These shared medium networks typically use time, frequency, or code division multiplexing to transport data signals from a central terminal to several remote customer terminals and Time Division Multiple Access (TDMA) to transport data signals from the remote terminals to the central terminal TDMA is characterized by non-continuous or burst mode data transmission. In existing optical networks, especially in a PON architecture, each packet of information from a remote terminal is multiplexed in a time sequence on one fiber and transmitted in a burst-like manner.
A PON generally uses wavelength division multiplexing (WDM), for example, using one wavelength for downstream traffic and another for upstream traffic on a particular single fiber. WDM can include, for example, Wide Wavelength Division Multiplexing, Coarse Wavelength Division Multiplexing (CWDM), and Dense Wavelength Division Multiplexing (DWDM).
An Ethernet passive optical network (EPON) is a PON that uses standard IEEE 802.3 Ethernet frames, for example, to encapsulate Internet Protocol (IP) traffic. Conventional EPON varieties include 1G EPON (supporting downstream and upstream speeds of 1 Gbps (gigabit per second)), 10G EPON (supporting downstream and upstream speeds of 10 Gbps), and 10G/1G EPON (supporting downstream speeds of 10 Gbps and upstream speeds of 1 Gbps). Other PON variations include Broadband PON (BPON), Gigabit PON (GPON), XGPON (also known as 10G-PON), and the like.
An EPON typically supports bidirectional communications between an Optical Line Terminal (OLT) and one or more Optical Network Units (ONUs). Downstream traffic is from the OLT to the ONUs, and upstream traffic is from the ONUs to the OLT. An ONU may, for example, be included in customer premises equipment (CPE), or installed at a customer or end-user site, such as a home or residence, a multiunit residential building, an office building or complex, or a business or workplace. A typical ONU converts optical signals (e.g., transmitted via fiber) to electrical signals, and vice versa.
In a typical configuration, an EPON hub includes one or more OLTs, each of which includes one or more EPON transceivers for optical signals. Each OLT includes one or more media access control (MAC) instances. The optical signals from each EPON transceiver are combined in a WDM combiner having one or more stages. A power splitter receives a single optical signal from the WDM combiner, and splits the signal to a plurality of optical fibers (each carrying many wavelengths). For example, a one-by-M (1×M) power splitter supports splitting the optical signal to M fibers. In another embodiment, the optical signals from each EPON transceiver bypass the WDM combiner and connected directly to the power splitter.
There is a need for an optical regeneration device that converts from the WDM/CWDM/DWDM domain to the EPON domain, resides in the node that connects the hub to the CPE, and provides a cost effective solution that is flexibly deployed. The advantages provided by the optical regeneration device of the present invention include enabling coexistence between PON signals and existing HFC services, increasing the optical link budget, increasing the geographic area that each OLT port can serve, increasing the number of subscribers who can be served by a single OLT port, and reducing the cost of the subscriber side optics. The presently disclosed invention satisfies these demands.